1. Field of the Invention
This invention relates to a semiconductor light-emitting device which can be driven with a low driving voltage and is high in light-extraction efficiency.
2. Description of the Related Art
There has been known a semiconductor light-emitting device which is constructed such that an n-type semiconductor layer, an active layer and a p-type semiconductor layer are successively laminated on a substrate and an ohmic electrode is attached to each of these semiconductor layers. In the case of the conventional light-emitting device which is provided with a reflective electrode for extracting light from the substrate side, Ag, which is high in reflectance, is generally employed as a reflective electrode material. Namely, while the reflectance of Ag is as very high as 96.6%, the reflectance of other metals that have been employed as an electrode likewise is very low, i.e. the reflectance of Au is 38.7%, the reflectance of Cu is 55.2%, and the reflectance of Ni is 41.2%.
However, when the reflective electrode consists of a single layer of Ag, not only the adhesion but also the ohmic property of the reflective electrode becomes poor, thereby making it difficult to manufacture a semiconductor light-emitting device having excellent properties.
In view of improving the adhesion and ohmic properties of this reflective electrode, there has been proposed a semiconductor light-emitting device wherein an Ni layer is interposed between the Ag layer and a nitride semiconductor layer (See for example JP-A 2000-294837).
However, in the case of the semiconductor light-emitting device proposed as described above, there is a problem that the reflectance is caused to decrease due to the interposition of the Ni layer, thereby making it difficult to fully utilize the excellent reflectance which Ag inherently has.